1. Field of The Invention
The present invention relates to a wafer, an apparatus and a method of chamfering a wafer, particularly a semiconductor wafer. The apparatus and method of chamfering a semiconductor wafer, includes chamfering a notch groove of the semiconductor wafer using a disc shape grindstone so as to form an edge of the wafer into a concave-shape in a pseudo manner.
2. Description of the Related Art
In a conventional apparatus and process for manufacturing a semiconductor device, a notch groove is formed by cutting a portion of the periphery of a semiconductor wafer into a V-shape or a circular-arc shape in order to easily align the orientation of crystal of the semiconductor wafer. The V-shape notch groove is widely employed due to enabling a limited area of the wafer to efficiently be used and having excellent locating accuracy.
In such a process for manufacturing the semiconductor device, the periphery of the semiconductor wafer sometimes comes in contact with a portion of an apparatus for use in the manufacturing process. Such a contact causes dust and a crack to occur. In order to prevent such a contact, the periphery of the semiconductor wafer is chamfered in general.
A conventional method of chamfering the notch groove is shown in FIGS. 15 and 16.
In FIGS. 15 and 16, the reference numeral 1 represents a wafer; 3, notch groove; 10, a formed grindstone 10; 11, a grindstone shaft.
The phrase xe2x80x9cformed grindstonexe2x80x9d means a grindstone having a grinding surface a cross-section which is substantially the same as the ground portion of the wafer 1 after grinding operation, as shown in FIG. 15. At this time, the formed grindstone 10 is formed into a hand-drum shape.
As shown in FIG. 15, the formed grindstone 10 is a rotatable grindstone having a bus line 10a and rotates around grindstone shaft 11. The bus line 10a of the formed grindstone 10 is formed into a concave shape corresponding to a convex bus line of the wafer. The notch groove 3 formed into a substantially V-shape in preprocess comprises straight portions 3a, a groove bottom 3b, and orifices 3c as shown in FIG. 16. The notch groove 3 is chamfered by the formed grindstone 10 as shown in FIG. 16 . A curvature radius r (a diameter d) in the center of the formed grindstone 10 is smaller than that of a groove bottom 3b of the notch groove 3.
The chamfering process is performed by chamfering the notch groove 3 as drawing such a tool locus 13 shown in FIG. 16 by the formed grindstone 10 while the grindstone shaft 11 is being maintained to be in parallel with the center line of the wafer 1.
The notch grooves of the wafer before/after chamfering is performed are shown respectively in FIGS. 17 and 18. A surface 3f of the wafer 1 shown in FIG. 17 is chamfered by formed grindstone 10 so as to form chamferings C1, C2 and C3 as shown in FIG. 18.
Since the straight portion 3a of the notch groove 3 is brought into contact with a locating pin having a diameter of about 3 mm and the groove bottom 3b has a small curvature radius, the diameter d of the formed grindstone 10 is about 2 mm. Therefore, the grindstone is rotated at about 100,000 rpm to realize required grinding speed.
Further, since the diameter of the grindstone is small, a metal-bond diamond grindstone is employed as the grindstone to prevent abrasion of the grindstone. The metal-bond grindstone, however, has a maximum surface roughness Rmax of 1 xcexcm which causes the wafer to sustain damage of about 10 xcexcm in the form of a crack layer and polishing such as buffing, which is performed as a following process, takes about 10 minutes.
Moreover, in order to subject the mirror-surface polishing/finishing process into the chamfered portion of the notch groove similar to the chamfered portion of the peripheral side surface of the disc shape wafer, surface roughness of the chamfered portion of the notch groove must be improved, that is grinding must be performed to realize surface roughness of about 0.1 xcexcm. A resinoid-bond grindstone is used so that the notch groove is chamfered to realize the surface roughness of about 0.1 xcexcm. However, the use of the resinoid-bond grindstone excessively causes abrasion of the grindstone and considerable deformation of the shape of the grindstone. Accordingly,the shape of the chamfered portion deteriorates.
Accordingly, an object of the present invention is to provide a wafer, an apparatus and a method of chamfering a notch groove of a wafer, in which the wafer is chamfered so as to have satisfied surface roughness of the formed notch groove and reduced abrasion of the grindstone.
According to a first aspect of the present invention, there is provided a method of chamfering a notch groove of a wafer formed into a disc shape, comprising the steps of:
using a wafer having a notch groove surface, means for holding the wafer, a grindstone frame incorporating a grindstone formed into a disc shape and structured such that a leading end of a radial-directional cross section of an peripheral side surface obtained by cutting with a plane including a grindstone axis has a curvature radius smaller than a minimum curvature radius of the notch groove and moving means which is capable of relatively moving the wafer and the grindstone along the notch groove of the wafer on a plane which is in parallel with the principal plane of the wafer and relatively moving substantially along the chamfering shape of the wafer on a plane intersecting the parallel plane;
(1) making the central line of the wafer and the central line of the grindstone to intersect each other;
(2) causing the grindstone to act on the notch groove such that a locus of a tool is drawn on a plane which is in parallel with the principal plane of the wafer to relatively move the grindstone and the wafer along the notch groove to perform chamfering along the notch groove;
(3) relatively moving the grindstone and the wafer on a plane intersecting the plane in accordance with a chamfered shape of the notch groove to allow the grindstone and the wafer to correspond to the notch groove in a portion except for the chamfered portion;
(4) causing the grindstone to act on the notch groove on a plane which is in parallel with the plane which is in parallel with the principal plane of the wafer and which is different from the plane such that a locus of a tool is drawn to relatively move the grindstone and the wafer along the notch groove to furthermore performing chamfering along the notch groove;
(5) relatively moving the grindstone and the wafer on a plane intersecting the plane in accordance with the chamfered shape of the notch groove to allow the grindstone and the wafer to correspond to the notch groove in a portion except for the chamfered portion; and
(6) similarly chamfering the notch groove into a polygonal shape.
According to a second aspect of the present invention, there is provided a method of chamfering a notch groove of a wafer formed into a disc shape, comprising the steps of:
using a wafer having a notch groove surface, means for holding the wafer, a grindstone frame incorporating a grindstone formed into a disc shape and structured such that a leading end of a radial-directional cross section of an peripheral side surface obtained by cutting with a plane including a grindstone axis has a curvature radius smaller than a minimum curvature radius of the notch groove and moving means which is capable of relatively moving the wafer and the grindstone along the notch groove of the wafer on a plane which is in parallel with the principal plane of the wafer and relatively moving substantially along the chamfering shape of the wafer on a plane intersecting the parallel plane;
(1) making the central line of the wafer and the central line of the grindstone to intersect each other;
(2) causing the grindstone to act on the notch groove such that a locus of a tool is drawn on a plane which is in parallel with the principal plane of the wafer to relatively move the grindstone and the wafer along the notch groove to perform chamfering along the notch groove;
(3) relatively moving the grindstone and the wafer on a plane intersecting the plane in accordance with a chamfered shape of the notch groove to allow the grindstone and the wafer to correspond to the notch groove at a position adjacent to the chamfered portion such that portions of the grindstone and the wafer overlap the chamfered portion;
(4) causing the grindstone to act on the notch groove such that a locus of a tool is drawn on a plane which is in parallel with the plane which is in parallel with the principal plane of the wafer and which is different from the plane to perform chamfering along the notch groove at a position adjacent to the chamfering;
(5) relatively moving the grindstone and the wafer on a plane intersecting the plane in accordance with the chamfered shape of the notch groove to allow the grindstone and the wafer to correspond to the notch groove at a position adjacent to the chamfered portion such that portions of the grindstone and the wafer overlap the chamfered portion; and
(6) similarly chamfering the notch groove into a polygonal shape.
According to a third aspect of the present invention, there is provided a method of chamfering a notch groove of a wafer formed into a disc shape, comprising the steps of:
using a wafer having a notch groove surface, means for holding the wafer, a grindstone frame incorporating a grindstone formed into a disc shape and structured such that a leading end of a radial-directional cross section of an peripheral side surface obtained by cutting with a plane including a grindstone axis has a curvature radius smaller than a minimum curvature radius of the notch groove and moving means which is capable of relatively moving the wafer and the grindstone along the notch groove of the wafer on a plane which is in parallel with the principal plane of the wafer and relatively moving substantially along the chamfering shape of the wafer on a plane intersecting the parallel plane;
(1) making the central line of the wafer and the central line of the grindstone to intersect each other;
(2) causing the grindstone to act on the notch groove and a circular peripheral side surface such that a locus of a tool is drawn on a plane which is in parallel with the principal plane of the wafer to relatively move the grindstone and the wafer at a position corresponding to the notch groove of the wafer and add rotation of the wafer such that the position of the grindstone is fixed at a position corresponding to the peripheral side surface of the wafer to perform chamfering along the notch groove and the circular peripheral side surface of the wafer;
(3) relatively moving the grindstone and the wafer on a plane intersecting the plane in accordance with chamfered shapes of the notch groove and the circular peripheral side surface to allow the grindstone and the wafer to correspond to the notch groove and the circular peripheral side surface of the wafer in a portion except for the chamfered portion;
(4) causing the grindstone to act on the notch groove and the circular peripheral side surface of the wafer on a plane which is in parallel with the plane which is in parallel with the principal plane of the wafer and which is different from the plane such that a locus of a tool is drawn to relatively move the grindstone and the wafer at a position corresponding to the notch groove of the wafer and add ratio of the wafer such that the position of the grindstone is fixed at a position corresponding to the peripheral side surface of the wafer to furthermore perform chamfering along the notch groove and the circular peripheral side surface of the wafer;
(5) relatively moving the grindstone and the wafer on a plane intersecting the plane in accordance with the chamfered shape of the notch groove and the circular peripheral side surface to allow the grindstone and the wafer to correspond to the notch groove and the circular peripheral side surface of the wafer in a portion except for the chamfered portion; and
(6) similarly chamfering the notch groove into a polygonal shape.
According to a fourth aspect of the present invention, there is provided a wafer comprising: a notch groove formed in a semiconductor wafer formed into a disc shape, wherein the notch groove is chamfered into a polygonal shape.
Note that a polygonal shape generally means a shape which comprises at least three straight lines. However, in this specification, the polygonal shape comprises at least three slightly curved bus lines, each of which defines the chamfered surfaces as clearly shown in FIG. 6.
According to a fifth aspect of the present invention, there is provided a wafer according to the fourth aspect, wherein chamfering of the notch groove is performed such that a plane which is in parallel with a center line of the wafer is included. In other words, as shown in FIG. 6 a slightly curved bus line defining the outermost chamfered surface C3 of the wafer 1 is substantially extended in parallel with the center line of the wafer 1.
According to a sixth aspect of the present invention, there is provided a wafer according the fourth aspect of the fifth aspect, wherein the polygonal shape has surfaces each of which is formed into a concave shape.
Further, the above-mentioned object can be achieved by a chamfering apparatus for a wafer with a notch groove, according to the present invention comprising:
a holder rotatably holding a wafer with a notch groove;
a grindstone frame rotatably supporting a disc shaped grindstone, the grindstone having a peripheral side surface at a leading end in its radial direction which has a curvature radius in a cross-section smaller than a minimum curvature radius of the notch groove, the cross section obtained by cutting with a plane containing the center axis of the grindstone, the central line of the wafer and the central line of the grindstone defining a skew line relationship;
moving member capable of relatively moving the wafer and the grind stone along the notch groove of the wafer on a parallel-extending plane which is in parallel with the principal plane of the wafer and relatively moving substantially along the chamfering shape of the wafer on an intersecting plane intersecting the parallel-extending plane at a predetermined angle; and
a controller controllable the relative movements between the wafer and the grindstone on the parallel-extending plane and the intersecting plane
wherein the controller
causes the grind stone to act on the notch groove while relatively moves the grindstone and the wafer in such a manner that a contact position therebetween is moved along the notch groove while a first tool moving locus is drawn on a first parallel plane which is in parallel with the principal plane of the wafer, to thereby perform chamfering a first chamfered portion along the notch groove;
relatively moves the grind stone and the wafer in such a manner that the contact position therebetween is moved in accordance with a chamfered shape of the notch groove so as to allow the contact position to correspond to a second chamfered portion of the notch while a second tool moving locus is drawn on a first intersecting plane intersecting the parallel-extending plane at the predetermined angle, the second chamfered portion being substantially different from the first chamfered portion thus chamfered;
causes the grindstone to act on the notch groove while relatively moves the grindstone and the wafer in such a manner that the contact position therebetween is moved along the notch groove while a third tool moving locus is drawn on a second parallel plane which is in parallel with the principal plane of the wafer and is different from the first parallel plane, to thereby perform chamfering the second chamfered portion along the notch groove; and
relatively moves the grind stone and the wafer in such a manner that the contact position therebetween is moved in accordance with the chamfered shape of the notch groove so as to allow the contact position to correspond to a third chamfered portion of the notch while a fourth tool moving locus is drawn on a second intersecting plane intersecting the parallel-extending plane at the predetermined angle, the third chamfered portion being substantially different from the first and second chamfered portions thus chamfered; and
causes the grindstone to act on the notch groove while relatively moves the grindstone and the wafer in such a manner that the contact position therebetween is moved along the notch groove while a fifth tool moving locus is drawn on a third parallel plane which is in parallel with the principal plane of the wafer and is different from the first and second parallel planes, to thereby perform chamfering the third chamfered portion along the notch groove, thereby chamfering the notch groove into a polygonal shape.
In the chamfering apparatus, it is preferable that the first intersecting plane is different from the second intersecting plane.
In addition, in the chamfering apparatus, the predetermined angle may be about 90 degrees.
Further, in the chamfering apparatus, it is advenatgeous that the controller controls the moving member in such a manner that the first and second chamfered portions are partially overlapped with each other, and also the second and third chamfered portions are partially overlapped with each other.
Furthermore, in the chamfering apparatus, it is preferable that the controller controls the moving member in such a manner that each of the first, second and third chamfered portions is continuously provided on the notch groove and a circular peripheral side surface of the wafer.
In this specification, the notch groove includes so-called an orientation flat shape as well as the V-shape (some what shape variation included).
According to the above-mentioned a wafer, an apparatus and a method of chamfering a notch groove of a wafer according to present invention,
(1) Since the grindstone having the large diameter can be used, the lifetime of the grindstone can significantly be elongated.
(2) Notch grooves having the same shape/predetermined shape can always be formed by controlling the outer diameter of the grindstone regardless of curvature radius of the leading end of grindstone, if the cross sectional shape of the leading end of grindstone, which obtained by cutting at a plane including the grindstone shaft, has a size such that the cross sectional shape thereof can contact with the bottom of the notch groove of the wafer.
(3) Since the problem of deformation of the formed grindstone (having a small diameter) adaptable to the cross sectional shape of chamfering does not arise, the lifetime of the grindstone can be elongated and the cross sectional shape of chamfering can always be obtained stably.
(4) The conditions under which grinding is performed to realize required surface roughness of the chamfered portion are not severe as compared with the conditions of grinding required when a formed grindstone (having a small diameter) is employed. Therefore, chamfering finishing by mirror-surface polishing/finishing process can be performed.
(5) A chamfering of the peripheral side surface of the wafer can be also performed by grinding continually after chamfering of the notch groove.